1. Field of the Invention
The present invention relates to a relaxation oscillator, and more particularly, to a relaxation oscillator capable of generating a ramp wave having a stable frequency while preventing a frequency from being changed due to a delay or an offset of a comparator by controlling a peak voltage of the ramp wave to be equal to a reference voltage by using a negative feedback loop.
2. Description of the Related Art
Recently, a power supply unit or a light emitting diode (LED) driver requires a high-efficiency DC-DC converter due to increased interest in the energy efficiency of electronics. In order to stably operate the DC-DC converter, it is necessary to use an oscillator having a stable frequency. Generally, the oscillator is a circuit generating output signals without input signals, which can generate various waveforms, such as a sine wave, a square wave, a triangular wave, a sawtooth wave, or the like.
In particular, the relaxation oscillator charges and discharges a capacitor at such time as a unique threshold voltage of circuits therein is reached, so as to generate oscillation signals. The relaxation oscillator includes a comparator for making a comparison with the threshold voltage. However, the comparator originally has an offset or a delay, such that the relaxation oscillator cannot provide a stable frequency.